The present invention relates to a clutch device for coupling two rotating bodies provided to be opposite each other almost concentrically to allow the bodies to rotate synchronously when rotational power is inputted from a first rotating body side, and for cutting off rotational power to the first rotating body when the rotational power is inputted from a second rotating body side.
In a conventional clutch device of this type wherein the first rotating body is driven to rotate by a power source such as a motor and this rotational power is transmitted to the second rotating body, when rotational power in counter direction is inputted from the second rotating body, a worm reduction gear or an electromagnetic brake is adopted as a mechanism for cutting off the transmission of the rotational power to the first rotating body (or cutting off inverse input).
In case of the worm reduction gear, the transmission efficiency of the first rotating body with respect to the second rotating body is low. Besides, since gear sound is generated by the engagement of a worm gear and a worm, the clutch device is inferior in soundless characteristics.
In case of the electromagnetic brake, the supply of power is required to perform a braking operation to thereby push up operation costs and a complex electronic control circuit is required to control the supply of power to an electromagnetic coil which controls the transmission timing of rotational power to thereby push up production costs.
Moreover, in either case, there is a limit to the intent to provide a lighter clutch device.
It is, therefore, an object of the present invention to provide a clutch device excellent in transmission characteristics for the rotational power of the first rotating body, excellent in soundless characteristics, capable of greatly reducing costs by being constituted out of a simple structure and capable of realizing a lightweight.
According to the present invention, a clutch device for coupling two rotating bodies provided to be opposite each other almost concentrically so as to be synchronously rotatable when rotational power is inputted into a first rotating body out of the two rotating bodies, and for cutting off rotational power to the first rotating body when the rotational power is inputted into a second rotating body out of the two rotating bodies, is characterized by comprising: a movable frictional member rotatable synchronously with the second rotating body, and attached to be displaceable in an axial direction; a fixed frictional member fixedly arranged at a position at which the movable frictional member is press-contacted with or separated from the fixed frictional member depending on a displacement of the movable frictional member in the axial direction; and a cam mechanism for separating the movable frictional member from the fixed frictional member, integrating the first rotating body, the movable frictional member and the second rotating body with one another and coupling the first and second rotating bodies to be synchronously rotatable when the first rotating body rotates, and for press-contacting the movable frictional member with the fixed frictional member, integrating the second rotating body, the movable frictional member and the fixed frictional member with one another and turning the second rotating body into an irrotational state when the second rotating body rotates.
According to the present invention, the movable frictional member, the fixed frictional member and the cam mechanism can transmit the rotational power of the first rotating body to the second rotating body with high efficiency and the structure becomes simple to thereby make it possible to reduce operation and production costs.
According to the present invention, in the above-stated improved clutch device, the movable frictional member has an outer peripheral surface consisting of an annular plate formed into a tapered surface which diameter becomes larger toward one side in the axial direction; the fixed frictional member has an inner peripheral surface formed as a tapered surface which diameter becomes larger toward one side in the axial direction, and has an inner peripheral surface consisting of a cylindrical body concentrically provided on the outer peripheral surface of the movable frictional member; and if the movable frictional member is displaced in the axial direction, the tapered outer peripheral surface of the movable frictional member is turned into a state of being press-contacted with or separated from the tapered inner peripheral surface of the fixed frictional member.
In this case, since the clutch device has a simple structure in which the movable frictional member is press-contacted with or separated from the fixed movable frictional member on the tapered surfaces of the movable frictional member and the fixed frictional member, the operation and production costs of the clutch device can be reduced.
According to the present invention, in the above-stated improved clutch device, the cam mechanism includes cam grooves provided on respective opposite surfaces of the first rotating body and the movable frictional member, and a clutch ball inserted between the cam grooves. The clutch ball rolls in the cam grooves in circumferential direction to thereby displace the movable frictional member to be press-contacted with or separated from the fixed frictional member.
In this case, since the cam mechanism consists of the cam grooves and the clutch ball, the rotational power of the first rotating body can be transmitted to the second rotating body with high efficiency and the structure becomes simple to thereby make it possible to reduce operation and production costs.
According to the present invention, in the above-stated improved clutch device, the cam mechanism includes a pair of cam grooves respectively provided on opposite surfaces of the first rotating body and the movable frictional member and a cam-shaped convex portion. The cam-shaped convex portion rolls in the cam grooves in circumferential direction, to thereby displace the movable frictional member to be press-contacted or separated from the fixed frictional member.
In this case, since the cam mechanism consists of the cam grooves and the cam-shaped convex portion, the rotational power of the first rotating body can be transmitted to the second rotating body with high efficiency and the structure becomes simple to thereby make it possible to reduce operation and production costs.
According to the present invention, in the above-stated improved clutch device, an urging member for elastically urging the movable frictional member toward a side of being press-contacted with the fixed frictional member, is attached.
In this case, since the clutch device has a structure of press-contacting the movable frictional member with the fixed frictional member using the urging member, the synchronous rotating operation of the first rotating body and the second rotating body and the separating operation of separating the second rotating body from the first rotating body can be performed more smoothly.